Search results for "spin [structure function]"
showing 10 items of 1132 documents
Spin crossover and photomagnetism in dinuclear iron(II) compounds
2007
Abstract In this paper, we review recent work reported in the field of molecular spin crossover phenomena in dinuclear compounds. Following a comprehensive overview on the synthesis and properties of new iron(II) dinuclear compounds presenting the spin crossover phenomenon, we focus this review on recent efforts made in studying and understanding the photo-physical properties of the {[Fe(L)(NCX)2]2bpym} (L = bt or bpym, X = S or Se) family of compounds. Finally, literature on the different theoretical approaches treating the static and dynamic properties of dinuclear complexes presenting two-step thermal spin transition is briefly summarized.
A Novel Dinuclear Fe II Spin‐Crossover Complex Based on a 2,2‐Bipyrimidine Bridge Ligand: [Fe(CH 3 bipy)(NCS) 2 ] 2 bpym
2004
The dinuclear iron(II) complex {[Fe(CH3bipy)(NCS)2]2bpym} has been synthesised and its crystal structure determined at 293 K. The magnetic properties display intramolecular antiferromagnetic coupling at 1 bar (J = −4.2 cm−1), and the onset of a pressure-induced spin conversion is observed at 11 kbar. Magnetic field Mossbauer measurements have been carried out at 4.2 K, and indicate that the HS species correspond to [HS-HS] pairs. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Towards Molecular Conductors with a Spin‐Crossover Phenomenon:Crystal Structures, Magnetic Properties and Mössbauer Spectra of[Fe(salten)Mepepy][M(dm…
2005
Three new iron(III) compounds of formula [Fe(salten)Mepepy][M(dmit)2]·CH3CN (M = Ni, Pd, Pt; H2salten = 4-azaheptamethylene-1,7-bis(salicylideneiminate); Mepepy = 1-(pyridin-4-yl)-2-(N-methylpyrrol-2-yl) ethane; dmit2– = 1,3-dithiole-2-thione-4,5-dithiolato) have been synthesised and the crystal structure of each compound has been solved at different temperatures. The structures consist of alternating layers of [M(dmit)2]– units and [Fe(salten)Mepepy] cations. In the Ni compound photo-isomerisation of the Mepepy ligand can be observed in dichloromethane solution. The temperature dependence of the magnetic susceptibility of the compounds reveals a gradual S = 5/2 blabla S = 1/2 spin crossove…
Cooperativity in the Iron(II) Spin-Crossover Compound [Fe(ptz)6](PF6)2 under the Influence of External Pressure (ptz = 1-n-Propyltetrazole)
1997
The iron(II) spin-crossover compound [Fe(ptz)(6)](PF(6))(2) (ptz = 1-propyltetrazole) crystallizes in the triclinic space group Ponemacr;, with a = 10.6439(4) Å, b = 10.8685(4) Å, c = 11.7014(4) Å, alpha = 75.644(1) degrees, beta = 71.671(1) degrees, gamma = 60.815(1) degrees, and Z = 1. In [Fe(ptz)(6)](PF(6))(2), the thermal spin transition is extremely steep because of cooperative effects of elastic origin. The transition temperature at ambient pressure is 74(1) K. An external pressure of 1 kbar shifts the transition temperature to 102(1) K, corresponding to a stabilization of the low-spin state, which is smaller in volume. The volume difference between the high-spin and the low-spin stat…
Crystal structure, magnetic properties and Mössbauer studies of [Fe(qsal)2][Ni(dmit)2]
2007
Abstract A new compound of formula [Fe(qsal)2][Ni(dmit)2] (1) has been synthesised, structurally and magnetically characterised (qsalH = N-(8-quinolyl)salicylaldimine, dmit2− = 1,3-dithiol-2-thione-4,5-dithiolato). Its structural features and its magnetic behaviour were compared with those of [Fe(qsal)2]-based complexes, and more particularly [Fe(qsal)2][Ni(dmit)2] · 2CH3CN.
Thermal and Light-Induced Spin Transition in the High- and Low-Temperature Structure of [Fe0.35Ni0.65(mtz)6](ClO4)2
1996
The thermal and light induced spin transition in [Fe(0.35)Ni(0.65)(mtz)(6)](ClO(4))(2) (mtz = 1-methyl-1H-tetrazole) was studied by (57)Fe Mössbauer spectroscopy and magnetic susceptibility measurements. In addition to the spin transition of the iron(II) complexes the compound undergoes a structural phase transition. The high-temperature structure could be determined by X-ray crystallography of the isomorphous [Fe(0.25)Ni(0.75)(mtz)(6)](ClO(4))(2) complex at room temperature. The X-ray structural analysis shows this complex to be rhombohedric, space group Rthremacr;, with a = 10.865(2) Å and c = 23.65(1) Å with three molecules in the unit cell. The transition to the low-temperature structur…
Synthesis, crystal structure, magnetic properties and 57Fe Mossbauer spectroscopy of the new trinuclear [Fe3(4-(2'-hydroxyethyl)-1,2,4- triazole)6(H2…
2000
Hyetrz = 4-(2prime-hydroxyethyl)-1,2,4-triazole represents the first structurally characterized iron(II) spin crossover compound for which the structure has been solved above and below room temperature in both spin states. The compound crystallizes in the trigonal system, space group R3, a = 12.763(1) b= 67.144(1), V = 1684.3(1) 3, Z = 6 at 120K. At 330K the space group is retained and a = 13.0183(3) b=67.376(3), V = 1805.8(1) 3. The molecular structure consists of trinuclear FeII entities linked together by an unprecedented three-dimensional network of hydrogen bonds. This compound shows a gradual spin crossover behavior centered around room temperature, which has been followed by temperat…
Mononuclear Complexes of Iron(II) Based on Symmetrical Tripodand Ligands: Novel Parent Systems for the Development of New Spin Crossover Metallomesog…
2011
The synthesis and characterization of a series of mononuclear tripodand-based FeII complexes by means of Mossbauer andUV/Vis spectroscopic as well as magnetic methods is reported. The complexes were obtained from the reactions of FeII salt with heterocyclic aldehydes (imd = imidazole-4(5)-carboxaldehyde, py = picolinaldehyde, or 6-Mepy = 6-methylpicolinaldehyde) and a symmetric triamine [tren = tris(2-aminoethyl)amine, tame = 2,2,2-tris(aminomethyl)ethane, or tach = 1,3,5-cis,cis-cyclohexanetriamin]. Because of extreme rigidity of the capping triamine tach, the molecular structure of {Fe[tach(imd)3](BF4)2} (1) features an unprecedented tapered trigonal prismatic FeN6 polyhedron. The molecul…
Pressure Effect Studies on the Spin‐Transition Behavior of a Dinuclear Iron(II) Compound
2013
Magnetic studies into the effect of different hydrostatic pressures between ambient and 1.03 GPa on the high-spin (HS) i low-spin (LS) transition behavior of the dinuclear iron(II) compound [Fe II 2(PMAT)2](BF4)4·DMF (1, PMAT = 4-amino3,5-bis{[(2-pyridylmethyl)amino]methyl}-4H-1,2,4-triazole, DMF = N,N-dimethylformamide) have been carried out at 2– 300 K. Under ambient pressure, the sample studied exhibits a [HS–HS] to [HS–LS] half spin transition (ST) at T½ = 208 K without any thermal hysteresis. Increasing the pressure above 0.2 GPa causes an increase (initially rapid but above 0.5 GPa more gradual) of T½ as well as a matching reduction in the residual high-spin fraction at room temperatu…
Iron(II) Spin Transition Complexes with Dendritic Ligands, Part I
2008
The ligands G1- and G2-oligo (benzyl ether) (PBE) dendrons and their iron(II) complexes [Fe(Gn-PBE)3]A2·xH2O (with n = 1, 2 and A = triflate, tosylate) were prepared. The magnetic properties of the complexes were investigated by a SQUID magnetometer. All complexes exhibit gradual spin transition below room temperature. At very low temperatures the magnetic behaviour reflects zero-field splitting (ZFS) effects. 57Fe-Mossbauer spectroscopy was performed to distinguish between ZFS of high spin species and spin state conversion into the low spin state. Further characterisation was carried out by thermogravimetric analysis (TGA) and FT-IR spectroscopy. Structural features have been determined by…